Insight into the effects of reaction conditions on metal-free surface-initiated atom-transfer radical polymerization of methyl methacrylate from SBA-15

Mesoporous silica nanoparticles/polymer hybrid materials were prepared via metal-free surface-initiated atom-transfer radical polymerization (SI-ATRP). Self-synthesized mesoporous SBA-15 with surface hydroxyl groups was modified with (3-aminopropyl)-triethoxysilane, followed by anchoring of the ATRP initiator α-bromoisobutyryl bromide onto the surface via amide reaction. The SI-ATRP of methyl methacrylate was then carried out with fluorescein (FL) as a photocatalyst and trimethylamine (TEA) as an electron donor under irradiation with blue light. Thus, polymer chains grew directly from mesoporous walls. The hybrid materials were characterized by gel permeation chromatography, N 2 adsorption/desorption measurements, and thermogravimetric analysis. The effects of the ligand/photocatalyst molar ratios, solvent, and the monomer/initiator molar ratios on grafting density, molecular weight, and molecular-weight distribution were investigated. The results show that a higher TEA/FL ratio led to a higher reaction rate and better controllability of the polymerization but also to a lower grafting density. These properties were also affected by the solvent. With an increasing monomer/initiator molar ratio, the grafting rate, molecular weight, and grafting density exhibited increasing trends.